Contact bands for rockets



Jan. 16, 1962 R. A. WEINHARDT ET AL 3,016,588

CONTACT BANDS FOR ROCKETS Filed April 5, 1957 INVENTORS PAUL T. BA ES ROBERT A. INHARDT ORNEYS United States Patent i The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

The present invention relates to a method of forming electrical contact bands on tubular bodies and more particularly to forming contact bands on tubular bodies such as rockets that require a continuous electrical contact band around the periphery of the rocket to permit electrical contact with the electrical system of a rocket launcher regardless of the rotatable position that the rocket may assume in the launcher.

The invention involves a moulding technique for forming electrical contact bands on tubular bodies as rockets. Previously, contact bands were provided on rockets by methods such as axially sliding metallic hoops into place over suitable insulation and subsequently fastening the hoops into position, and also by Wrapping metallic strips over suitable insulation around a rocket tube, then fastening the ends of the strips together and fastening the resulting hoops into place, Both of the old methods require fastening of a lead wire from the internal electrical circuits to the hands by welding, soldering, brazing or some mechanical means, and the material of the band needs to be protected from corrosion either by the use of non-corrodible metals which are expensive or by plating. In general, these older methods of providing electrical contact bands have the disadvantage of requiring numerous operations to assemble, being expensive, and, in a varying degree, lacking reliability.

It is therefore an object of the invention to provide a new method of forming continuous electrical contact bands on tubular bodies such as rockets.

Another object of the invention is to provide a fast, reliable and inexpensive method of forming continuous electrical contact bands on tubular bodies such as rockets.

A further object of the invention is to provide a method of forming continuous electrical contact bands on tubular bodies such as rockets by injection moulding.

These and other objects and many of the attendant advantages of this invention will be readily appreciated as the same become better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

FIG. 1 is a side view, partially in cross-section, of a portion of the tubular body of a rocket showing the contact bands thereon;

FIG. 1A is an enlarged view of the portion of FIG. 1 which shows the cross-section of the contact bands on the rocket body;

FIG. 2 is a front view of a two-piece mould used in forming contact bands on the tubular rocket body;

FIG. 3 is a side view of the mould of FIG. 2 taken in the direction of the arrow 3;

FIG. 4 is a top view of the bottom half of the mould of FIG. 2, taken along the line 4-4;

FIG. 5 is a cross-sectional view of the half-mould taken along the line 5--5 of FIG. 4.

Referring now to the drawings, like numerals refer to like parts in each of the figures of drawing. The invention comprises bands 10, as in FIGS. 1 and 1A, formed by injection moulding a molten metallic alloy about an insulation 12 which surrounds the tubular portion 14 ice of a rocket. A mould, such as mould 16, FIG. 2, is clamped about insulation 12 which surrounds portion 14 of a rocket and a molten, relatively low melting point alloy is injected through openings 19, FIGS. 3 and 4, into the mould at 400 to 1600 psi. An example of an alloy which can be used for injection moulding electrical contact bands consists of lead, 15% antimony and 5% tin, and has a melting point of 522 F. Insulation 12 and lead wire 18 are placed in position prior to injecting the contact band metal into the mould 16 at openings 19. One end of lead wire 18 is positioned to project above insulation 12 but below the ultimate outer surface of the contact band.

The present invention provides a solid continuous band of metal formed without joints and which is electrically connected to the lead wire without soldering, brazing or welding, and without any additional mechanical fastening. The electrical connections are wholly enclosed in the contact band metal and protected from any type of corrosion. Since the solidification of the contact band is accompanied by shrinkage of the metal, the band 10 is held tightly to the insulation 12 and to the lead wire 18. The shrinking of the metal obviates the need for any additional fastening means. An additional advantage resulting from the use of the lead base alloy is that it will withstand corrosive atmospheres without the protection of any plating or chemical treatment. Further, the metal is relatively soft and allows appropriate electrical connections thereto by having the rocket launcher contact points dig into the band to etfect secure and reliable electrical contact. The forming of the band, fastening it in place, and establishing contact with the lead Wire can be performed in one operation in a very short time.

Other variations in construction are possible without departing from the principles of this invention. For example, the mould cavity may take many configurations; it may provide for forming all sides of the band except that which lies against the outer diameter of the insulation or merely the side which must eventually be exposed to contact the launcher connector by grooving the insulation to form the other sides. The lead wire 18 may enter the contact band from the bottom or any other side. The insulation may be of any suitable material, however, it has been found desirable to use a relatively soft rubber which permits the band to partially embed itself into the insulation upon shrinkage of the metal alloy thereby improving the bond between the band 10 and insulation 12, Further, soft rubber permits the forked grooves 17 of the mould 16 to bite into the insulation forming a good seal to prevent side flow of the molten metal alloy when injected into the mould for casting the contact bands; when the mould is removed the soft rubber returns to its normal shape.

Many alloys may be used for the contact band material providing that the melting point not be so low as to allow undue weakening at high operating temperatures, nor so high as to cause damage to the insulation during the injection procedure; the coefficient of thermal expansion should be reasonably close to that of the rocket material so as not to be loosened nor tightened to the point of cracking by temperature extremes; the composition should be such as to resist corrosion or if corrosive, the corrosion products should not be electrically insulative.

Obviously, many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that the scope of the invention is to be restricted only by the scope and limitations of the appended claim and not by the details of the illustrative example specifically de' scribed hereinabove.

What is claimed is:

A method for forming an external insulated contact band about a tubular body portion of a rocket and connecting said band electrically to the interior of said body comprising the steps of forming an annular groove in the exterior surface of said body, forming a radial hole in said body into said groove, placing an annular band of insulating material into said groove, forming a groove in said band of insulating material, pushing the bared uninsulated end of an otherwise insulated lead wire through said radial hole and said band of insulated material from the inside of said tube so that said uninsulated end of said wire extends slightly into the groove in said insulating band, placing the assembly in a mould which is clamped around the band of insulation at spaced annular planes at opposite sides of said bared end of lead wire and thus provides an annular mould cavity between said planes, and injecting a molten relatively low melting point alloy into said mould cavity to form a contact band which is in electrical contact with said bared end of said lead wire, and which binds said insulating band tightly to said tube as it contracts upon cooling. 2O

References Cited in the filetof this patent UNITED STATES PATENTS OTHER REFERENCES Campbells List of Alloys, published by the American Society for Testing Materials, 1930, p. 48.

Worth: Abstract of application Ser. No. 702,720, published July 12, 1949 in 624 0.6. 638.

Metals and Alloys, by the Technical Staff of Metal Industry, Chemical Publishing Co., Inc., 1950, pp. 86, 124,131,193. 

